No. 2133: Lightning Strike

Garfield: Some people say I'm mean to Odie. Don't get me wrong, I love dogs. And if I'm lying, may lightning strike...
Garfield {looking up in horror}: ...me.
{Garfield and Jon are at the vet, and Liz is wrapping Garfield in a body cast.}
Jon: How long will he be in that body cast, Doc?
Liz: About a week.
Garfield: I could've guessed as much.

The author writes:

I was originally planning on editing a panel from 1994-07-10 for the punchline, but then I came across 1980-10-27 and figured it would work better.